The present invention relates to a method and apparatus for monitoring the functioning of testing devices in machines or production lines for the making and/or processing of rod-shaped articles which constitute or form part of smokers' products. Such articles may constitute filter cigarettes, cheroots, cigars or cigarillos, plain cigarettes, cheroots, cigars or cigarillos and/or filter rod sections. For the sake of convenience, the following description will refer primarily to filter cigarettes with the understanding, however, that the method and apparatus of the invention can be resorted to with equal advantage in connection with the manufacture and/or processing of other rod-shaped articles which constitute or form part of smokers' products.
In a filter tipping machine, filter cigarettes of unit length or multiple unit length are caused to advance along a predetermined path, normally at right angles to their axes, and past one or more testing devices which ascertain whether or not the filter cigarettes exhibit defects of any one of several types, such as open seams, holes in their wrappers, frayed ends of wrappers, unsatisfactory permeability of selected portions of wrappers (especially wrapers of filter plugs), unsatisfactory density of the tobacco-containing ends, absence of tobacco-containing or filter-containing portions and/or a combination of these. As a rule, cigarettes which are produced in the filter tipping machine travel along a predetermined path and at a predetermined distance from one another, i.e., successive filter cigarettes are separated from each other by spacings or gaps of predetermined width. If a testing device detects a defective or presumably defective filter cigarette (depending upon whether or not the operation of the testing device is reliable), it generates a defect signal which is transported, in imitation of forward movement of the respective filter cigarette, to a segregating station where the defective or presumably defective filter cigarette is ejected from the path so that it cannot reach the consumer. Defect signals can be said to constitute signals of a first type in contrast to signals of a second type (e.g., zero signals or no signals) which are indicative of (presumably) satisfactory or acceptable filter cigarettes. The defect signals must be delayed between a given testing station and the segregating location because, even though a modern filter tipping machine produces very large quantities of filter cigarettes per unit of time, undelayed transmission of a defect signal from a testing device to the location where the defective or presumably defective cigarette is to be expelled from the path would take up only a minute fraction of time that is needed to advance the corresponding filter cigarette from the testing device to the segregating station.
Apparatus of the above outlined type operate quite satisfactorily as long as the testing devices are capable of reliably detecting all filter cigarettes which exhibit the defects that can or should be detected by the respective testing devices. In other words, one must simply assume that the testing devices operate properly and that each filter cigarette which has been found to be defective for one or more reasons must be segregated from the remaining articles downstream of the testing stations and prior to entering that portion of the path from which the filter cigarettes cannot be readily withdrawn for the purpose of preventing defective cigarettes from reaching the consumer.
The path along which the filter cigarettes advance sideways toward, past and beyond the testing station or stations, and along which the satisfactory and defective filter cigarettes advance toward and past the segregating station (and along which the satisfactory filter cigarettes advance beyond the segregating station) can be defined by a variety of conveyors, e.g., by rotary drum-shaped conveyors having axially parallel peripheral flutes for reception of discrete filter cigarettes or of several coaxial rod-shaped articles. As a rule, the distance between successive filter cigarettes which advance toward, past and beyond the testing station or stations and thereupon toward, past and (as far as satisfactory filter cigarettes are concerned) beyond the segregating station is uniform or practically uniform so that it takes a given interval of time for each filter cigarette to advance from its momentary position to the position then occupied by the immediately preceding filter cigarette, and so forth. Since the speed at which the filter cigarettes are transported sideways depends on the machine speed, and the machine speed determines the frequency at which the filter cigarettes are tested at one or more stations and (the defective filter cigarettes) ejected at the segregating station, it can be said that the rate at which the filter cigarettes advance along successive path sections of predetermined length determines the rhythm of operation of the machine or of a production line consisting of a group of interconnected machines for the making and/or processing of rod-shaped articles which constitute or form part of smokers' products.
The criteria or characteristics of filter cigarettes which the various testing devices monitor must be detected with a high degree of accuracy because a filter cigarette is considered defective and must be segregated from other filter cigarettes even if certain of its characteristics deviate rather slightly from the prescribed optimum characteristics. Such criteria or characteristics are monitored by various testing devices which, in the case of filter cigarettes, normally include a device for determination of the presence or absence of open seams, holes, frayed ends and/or like defects in the wrappers of filter cigarettes; a device for detecting the permeability of selected portions of wrappers in order to ascertain whether or not such selected portions can admit requisite quantities of cool atmospheric air into the column of tobacco smoke that flows into a smoker's mouth (the admission of atmospheric air is presumed to reduce the deleterious effects of nicotine and/or condensate upon the health of the smoker); a device for monitoring the density of tobacco-containing ends of filter cigarettes; and a device which monitors the presence or absence of any and all components or constituents of a filter cigarette (especially a device which ascertains the presence or absence of filter plugs). The testing device or devices of or for a filter tipping machine are installed downstream of some or all of the processing stations and such processing stations may include a station for placing pairs of plain cigarettes into axial alignment with one another in such a way that the plain cigarettes define a gap of predetermined width; a station where such gaps receive filter plugs of double unit length; a station where uniting bands are attached to successive groups of coaxial plain cigarettes and filter plugs; a station where the uniting bands are rolled around the respective groups so that each group constitutes a filter cigarette of double unit length; a station where successive filter cigarettes of double unit length are converted into filter cigarettes of unit length; and one or more additional stations.
The testing of various characteristics of filter cigarettes is desirable for a number of reasons. Thus, one can prevent defective filter cigarettes from reaching the consumers. Secondly, by ascertaining some or all of the defects, one can effect manual or automatic adjustments in a sense to eliminate the causes of such defects. Still further, the number of rejects can be held to a minimum if the defects are detected as quickly as possible, i.e., as close to the locus of the cause or causes of malfunctions as possible in view of the nature and mode of operation of a filter tipping machine. Thus, when one or more testing devices generate defect signals which entail a segregation of corresponding filter cigarettes from the satisfactory filter cigarettes, such defect signals can also be used for automatic, semiautomatic or manual regulation of various operations in the region or regions where the causes of malfunction and the resulting defects occur.
Segregation of defective filter cigarettes can take place immediately at or immediately downstream of the testing device which is used to detect defective cigarettes. Thus, if the machine embodies two or more testing devices, defective filter cigarettes can be removed at two or more different locations. This is cumbersome in many instances because the means for gathering defective filter cigarettes occupy a substantial amount of space which is at a premium in all kinds of machines for the manufacture and/or processing of cigarettes, filter rod sections or the like. Therefore, it is preferred to provide a common segregating station for all defective or presumably defective filter cigarettes and to provide means for delaying the defect signals which are generated by various testing devices so that all such signals can be transmitted to a single segregating device which is located downstream of the last or rearmost testing device. A method and an apparatus for the practice of such method with a view to segregate defective filter cigarettes at one and the same station, in spite of the fact that the signals for ejection can be furnished by two or more testing devices are disclosed in German Offenlegungsschrift No. 21 13 841. The apparatus which is disclosed in this prior publication comprises a signal delaying system which receives defect signals from several testing devices and delays each defect signal in dependency on the distance between the segregating station and the respective testing device. For example, the delaying system can employ a shift register with a number of successive stages one of which receives defect signals from a first testing device, another of which receives defect signals from a second testing device, and so forth. This ensures that the interval of travel of a defect signal from any one of several testing devices to the last stage of the delaying system and hence to the segregating station always matches the interval of travel of the corresponding defective filter cigarette from the station where a defect was detected to the segregating station. Such synchronization of transport of defect signals and of the defective filter cigarettes to the segregating station is desirable and necessary in order to ensure that the segregating device will weed out only those filter cigarettes which have been found to be defective or which have been labelled as being defective by one or more testing devices upstream of the segregating station.
A drawback of the just discussed method and apparatus is that it is not possible to associate the segregated filter cigarettes with those testing devices which have caused the segregation of filter cigarettes, i.e., the defective or presumably defective filter cigarettes are segregated at one and the same station but there is no possibility of ascertaining which cigarette was segregated in response to a defect signal from a first testing device, which cigarette was segregated in response to a defect signal from a second testing device, and so forth. On the other hand, such association of segregated filter cigarettes with the corresponding testing devices would be desirable and advantageous because one could readily ascertain whether or not any given testing device operates properly by the simple expedient of gathering a certain number of filter cigarettes which were segregated in response to signals from a given testing device and thereupon subjecting the gathered cigarettes to an independent examination. Thus, one could ascertain whether or not a testing device is properly adjusted so that it invariably segregates or initiates the segregation of all filter cigarettes which exhibit a given defect as well as whether or not such testing device effects the segregation of acceptable cigarettes and/or permits unsatisfactory cigarettes to advance past aand beyond the segregating station.